The present disclosure relates generally to non-woven graft materials for use in specialized surgical procedures such as neurosurgical procedures, wound repair, oral surgery, dermal repair and regeneration, head and neck surgery, endonasal surgery and bone repair, methods for making the non-woven graft materials, and methods for repairing tissue such as neurological tissue using the non-woven graft materials. More particularly, the present disclosure relates to non-woven graft materials including at least two distinct fiber compositions composed of different polymeric materials, methods for making the non-woven graft materials and methods for repairing tissue in an individual in need thereof using the non-woven graft materials.
Neurosurgical procedures commonly result in the perforation or removal of the watertight fibrous membrane surrounding the brain known as the dura mater. In all of these cases, the tissue barrier surrounding the brain must be repaired in a watertight manner in order to prevent damage to cortical tissues and leakage of cerebrospinal fluid. Dura substitutes are therefore needed to repair dural defects, reestablish the barrier that encloses the cerebrospinal space, and prevent cerebrospinal fluid (CSF) leakage and infection.
Numerous materials are currently in use as dura substitutes, including autograft, allograft, xenograft, and non-biologic synthetic materials. An ideal dura substitute should adequately restore the continuity of the dura mater and prevent CSF leak while minimizing infection. The mechanical properties of the material should facilitate suturing and/or tacking, yet also mimic the compliance of natural dura to allow ease of draping over delicate cortical tissues. Furthermore, an ideal dura substitute will minimize local tissue inflammation and preferably encourage the infiltration of cells and vasculature to expedite the reconstruction of native dura without inducing undesired outcomes of fibrosis or cortical adhesions.
Autograft materials utilized in dura repair are commonly acquired from a patient's own pericranium or facia latae. These tissues are desirable due to their minimal inflammatory response and their similarity to native dura. However, the use of these grafts is limited by the poor availability and host-site morbidity of the autograft material. Alternatively, human tissue is commonly utilized in the form of allografts, which are obtained from cadaveric dura. This tissue can be collected, sterilized, and stored to provide greater availability of graft material to repair large dura defects. However, significant risk of disease transmission limits the use of allografts in contemporary neurosurgical settings.
Xenograft materials are also commonly utilized as dura substitute products. Xenogenic materials are derived from bovine or porcine sources and are available in the form of decellularized tissues of the pericardium, small intestinal submucosa, and dermis or in the form of processed materials synthesized from collagen-rich sources such as the bovine Achilles tendon. Like allografts, xenografts have an inherent risk of zoonotic disease transmission and the potential to incite allergic and inflammatory reactions. Many biologic grafts have the advantage of being fully remodeled, whereby the natural components of the graft (e.g. collagen) recruit cell infiltration and angiogenesis that participate in the restructuring of the graft material. However, the rate at which a biologic graft is remodeled and resorbed is not well controlled, such that graft degradation can occur prematurely. This mismatch between graft resorption and native tissue regeneration can result in thin, weak tissue in the dura defect. The mechanical properties of xenograft materials also vary greatly due to differences in material processing such as crosslinking and protein denaturation. Select products have limited mechanical strength as to only be suitable for use as only grafts without the option of suturing. Other xenograft materials, however, provide the tear resistance and tensile strength required for suturing.
Some bovine-derived collagen materials are crosslinked to provide the mechanical strength necessary for suture repair of a dural defect. This manipulation of the mechanical properties can result in undesirable effects in the handling of the material, leading to a dura substitute with decreased compliance. Furthermore, the crosslinking of the bovine-derived collagen material has been shown to interfere with the degradation expected of its biologic collagen composition, leading to prolonged presence at the implant site with poorly defined material resorption. For biologically derived dura substitutes, desirable mechanical properties for suturability and desirable resorption properties for tissue remodeling are often mutually exclusive.
Despite the range of existing dura substitute materials available in contemporary neurosurgical clinics, there remains a need for a dura substitute that offers improved handling characteristics, mechanical properties, and safety compared to biologically derived grafts. Non-biologic synthetic materials have been explored to overcome the limitations of biologic grafts, whereby material strength, resorption, and safety can be controlled with much greater precision. Despite these offerings, tissue response to synthetic grafts has yet to be fully explored. Synthetic grafts also fall short in their approximation of the mechanical properties of the dura mater, such that these materials often have poor handling that complicates their clinical use.
Based on the shortcomings of the current clinically available materials, there remains a need for an improved resorbable non-biologic dura substitute that provides better handling and ease of use and improves the local tissue response during reconstruction of the native dura.